Answer:
Amount of Niobium-91 initially
= 300/91 =3.2967mol
2040 years = 3 ×680 = 3 half-lives
therefore, amount left = 0.4121mol
mass of Niobium-91 remaining = 0.4121 ×91 =37.5g
Please give brainliest
The answer would be angles UVX and RSQ.
Hope this helps
Answer:
20) the answer is -43
21) the answer is 25
22)the answer is -5
Step-by-step explanation:
20) 
n=-7
p=-6
we have:

21) mp-(p-(m-n))
m= -1 n=-6 p=-10
-1*-10-(-10-(-1-(-6)))
10-(-10-(5))
10-(-15)
10+15=25
22) 
m=1 n=5
1- 
1- 2/2 -5
1-1-5 =-5